Interactive fixed and mobile satellite network

ABSTRACT

A communications system includes at least one low earth orbit first satellite (10), at least one second satellite (11) in other than a low earth orbit, and a ground segment (12) that includes a plurality of user transceivers (78, 80, 82, 84) and at least one gateway (76) coupled to a publicly-accessible terrestrial communications system, such as a PSTN and/or a fiber optic network. The first satellite includes a first transceiver for communication with the at least one gateway, a second transceiver for communication with at least one user transceiver, and a third transceiver for communication with the at least one second satellite. The first, second and third transceivers are switchably coupled together on-board the first satellite by on-board processors and a switching matrix for relaying a user communication between the at least one gateway and the at least one user transceiver via the at least one second satellite. The plurality of user transceivers can include a plurality of data processors which are interconnected into a network through the at least one first satellite. This network can be considered as a virtual network, and can have a mesh, star, or other topology. The user transceivers can be adapted to transmit and receive direct sequence, code division/multiple access communications. Transmission of signals to and from the user transceivers is accomplished by spreading a digital data stream (e.g., voice, data, image, video) with assigned spreading codes.

FIELD OF THE INVENTION

This invention relates generally to communications systems and, inparticular, to communications systems that employ one or more satellitesto direct user communications through the system.

BACKGROUND OF THE INVENTION

Satellite delivered individual services are emerging as a new globalenterprise. These systems utilize or are proposed to utilize manyindividual circuits routed through one satellite or a constellation ofmany satellites to effect communications. One value of the satellitesystem is that it provides ubiquitous coverage of large areas of theearth without the construction of ground-based infrastructure. Since therecent availability of portions of the frequency spectrum for theseservices, several proposals have been advanced by a number oforganizations. One proposal would use Time Division Multiple Access(TDMA), while several others would employ Code Division Multiple access(CDMA). A feature of the CDMA systems is an ability to share theavailable frequencies by co-frequency operation, while experiencing onlya percentage decrease in the capacity of each system.

Furthermore, Low Earth Orbiting Satellite (LEOS) systems, also referredto as Non-GSO (geosynchronous orbit) satellite systems, offer a newdimension in communications. For example, the LEOS systems can providediversity, as described in U.S. Pat. No. 5,233,626, issued Aug. 3, 1993,entitled "Repeater Diversity Spread Spectrum Communication System", toStephen A. Ames. Another capability provided by the LEOS systems is anability to interconnect users to a fixed point, typically referred to asa Public Switched Telephone Network (PSTN).

High capacity, fiber optic-based communications is currently beingdeployed world-wide, and in particular in the United States, to directlyconnect to subscribers in their homes. In addition to providingconventional voice communication capability, the fiber optic-basednetworks can also provide video and high speed data capabilities. Theproliferation of networked personal computers having multimediacapabilities can take advantage of the increased speed and capacityprovided by the fiber optic based networks. However, the significantcosts involved in providing fiber optic lines is not economical in everylocale, and it can be expected that large non-urban areas will not be ina position to benefit from the advantages provided by fiber opticnetworks within a reasonable period of time.

OBJECTS OF THE INVENTION

It is a first object of this invention to provide a system and a methodfor providing communications services to regions which are not currentlyeconomical to serve with fiber optics.

It is a further object of this invention to provide a satellite-basedcommunications system that provides, in addition to mobile and fixedvoice and data service, a capability to provide high speed video anddata service.

SUMMARY OF THE INVENTION

The foregoing and other problems are overcome and the objects of theinvention are realized by a communications system that is constructedand operated in accordance with this invention. The communicationssystem includes at least one low earth orbit first satellite, andpreferably a constellation of multiple low earth orbit repeatersatellites. The satellites of the constellation are preferably ininclined circular orbits operating at an altitude of less than 2000kilometers. The communications system also includes at least one, andpreferably a plurality of second satellites in other than a low earthorbit, such as a geosynchronous orbit. The communications system alsoincludes a ground segment having a plurality of user transceivers and atleast one gateway coupled to a publicly-accessible terrestrialcommunications system and/or to various private networks, such as a PSTNand/or a fiber optic network. The first satellite(s) include a firsttransceiver for communication with the at least one gateway, a secondtransceiver for communication with at least one user transceiver, and athird transceiver for communication with the at least one secondsatellite. The first, second and third transceivers are switchablycoupled together on-board the first satellite for relaying usercommunications, such as voice, data, image, and video, between the atleast one gateway and the at least one user transceiver via the at leastone second satellite.

The at least one first satellite further includes a first on-boardprocessor that is bidirectionally coupled to the first transceiver; asecond on-board processor that is bidirectionally coupled to the secondtransceiver; and a switching network that is bidirectionally coupled tothe first and second on-board processors and to the third transceiverfor selectively establishing communication paths between the first andsecond on-board processors and the third transceiver.

The plurality of user transceivers can include a plurality of dataprocessors which are interconnected into a network through the at leastone first satellite. This network can be considered as a virtualnetwork, and can have a mesh, star, or other topology. In a presentlypreferred, but not limiting embodiment of this invention, the usertransceivers are adapted to transmit and receive direct sequence, codedivision/multiple access (DS-CDMA) communications, wherein thetransmission of signals to and from the user transceivers isaccomplished by spreading a digital data stream (e.g., voice, data,image, video) with predetermined spreading codes.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-set forth and other features of the invention are made moreapparent in the ensuing Detailed Description of the Invention when readin conjunction with the attached Drawings, wherein:

FIG. 1 is a block diagram of a satellite-based communications system inaccordance with this invention;

FIG. 2 is a block diagram of one of the gateways illustrated in FIG. 1;

FIG. 3 illustrates a constellation of LEO satellites havinginter-satellite links with a constellation of GSO, MEO, or other, higherorbiting, satellites;

FIG. 4 illustrates various service types and their connectivity throughthe LEO and GSO satellite constellations;

FIG. 5 schematically illustrates various geographical regions havingextensive, medium, and non-existent fiber optic service; and

FIG. 6 schematically illustrates a plurality of data processors that areconnected directly and indirectly (through a satellite and gateway) to afiber optic network.

DETAILED DESCRIPTION OF THE INVENTION

Reference is made to FIG. 1 for illustrating an exemplary embodiment ofthis invention. At least one and preferably a plurality of satellites 10are provided in earth orbit. The satellites 10 may form a constellationof low earth orbit satellites (LEOS), such as a constellation of 48satellites orbiting at less than 2000 kilometers, such as about 1400kilometers, in several inclined orbital planes. The orbits may becircular, although the teaching of this invention is not limited for useonly with circular orbits. Coupled to the satellites 10 via uplink anddownlink RF signals and associated transceivers is a terrestrial orground segment 12. The satellites 10 operate so as to interconnectvarious elements of the ground segment 12 through different portions ofthe frequency spectrum via a plurality of RF transmitters and receivers(transceivers), on-board processors, and a switching matrix capable ofinterconnecting any one of the on-board processors to another. Aprovision is also made for coupling to other satellites of the sameand/or a different constellation though inter-satellite links (ISL),such as RF or optical links.

In the presently preferred embodiment of this invention the satellites10 include circuitry 14 and antennas 16 and 18 for providinginter-satellite links with other satellites 11, such as ahigher-orbiting geosynchronous orbit (GSO), medium earth orbit (MEO), orMolniya constellation of satellites. In this manner a givencommunication signal can be uplinked from a portion of the groundsegment 12 to one of the satellites 10, and can then be routed throughone or more other satellites 11 before being downlinked back to theground segment 12, either directly or through another LEO satellite 10.This link may be bidirectional (e.g., full duplex).

The antennas 16 and 18 may be either non-deployed phased arrays ordeployed reflectors with multiple beam feed assemblies located in areflector focal plane.

Describing FIG. 1 now in greater detail, the satellite 10 includes anS-band receive antenna 20, an S-band transmit antenna 22, an L-bandreceive antenna 24 and an S-band transmit antenna 26. S-band antennas 20and 22 may operate at frequencies of 2.2 and 1.9 GHz, respectively, witha bandwidth of 30 MHz. The L-band antenna 24 may operate at 1.6 GHz,while the downlink S-band antenna 26 may operate at 2.5 GHz. Theantennas 20 and 22 may be either non-deployed phased arrays, deployedphased arrays, or deployed reflectors with multiple beam feeds locatedat the focal plane of the reflector. The bandwidth of the L-band andS-band transmissions through antennas 24 and 26 may be 16.5 MHz. Coupledto antennas 20-26 are respective RF circuit blocks 28-34 respectively.The RF circuit blocks 28-34 include suitable signal modulators anddemodulators, as appropriate. A presently preferred access techniqueemploys a direct sequence (DS), code division/multiple access (CDMA)technique. This invention is not, however, limited to only a DS-CDMAapproach. By example, a suitable time division/multiple access (TDMA)technique can also be used.

In the case of DS-CDMA, each RF circuit block includes circuitry forphase demodulating and despreading received communications usinguser-assigned pseudo-noise (PN) spreading codes to separate a pluralityof user signals that occupy a same portion of the bandwidth of theuplinked RF signal. The result is a plurality of digital data streamsthat are input to an on-board processor (OBP) 36 for processing androuting. Transmission of signals to the users is accomplished byspreading a digital data stream (e.g., voice, data, image, video) thatis received from the OBP 36 with assigned spreading codes, and thenphase modulating the spread communications prior to transmission.

Bidirectionally coupled to the S-band antenna/RF block pair 20, 22, 28and 30 is the first on-board processor (OBP) 36. Coupled to the L-band,S-band antenna/RF block pair 24, 26, 32 and 34 is a second on-boardprocessor 38. As was indicated above, the on-board processors 36 and 38receive communications signals that have been down-converted to basebandand demodulated (i.e., taken down to bits) within the respective RFblocks 28 and 32. Routing and other information within thecommunications, for example destination addresses associated with datapackets of speech, video, or data, is examined by the OBP fordestination and other information, and is thence routed through aninterconnector-router (ICR) block 70 to another OBP for completing arequired circuit. The ICR block 70 can be comprised of a cross-bar orsimilar switching arrangement that is programmed by the OBPs so as toestablish and maintain non-blocking communication paths between itsvarious input and output (I/O) ports 70a-70f. The ICR block 70 is thusable to controllably route communication signals to and from the variousones of the OBPs and also, if provided, other satellites 10 via theinter-satellite links block 14 and its associated antennas 16 and 18,via the satellite(s) 11. This interconnection capability enables avariety of ground segment terminal and equipment types to be coupledtogether, and to be coupled to an underlying communicationsinfrastructure (e.g., PSTN and/or fiber optic network) through one ormore satellites 10 and/or 11.

The satellite 10 further includes a first Ka-band (user-link) transmitantenna 40, a first Ka-band (user-link) receive antenna 42, a secondKa-band (feederlink) transmit antenna 44, and a second Ka-band(feederlink) receive antenna 46. The Ka-band antennas may operate atabout 19 GHz (receive) and about 28 GHz (transmit), bandwidth 400 MHz,and provide the high speed, high capacity user links that are a featureof this invention. These antennas may be either non-deployed phasedarrays, deployed phased arrays, or deployed reflectors with multiplebeam feeds located at the focal plane of the reflector. Coupled toantennas 40-46 are respective RF circuit blocks 48-54 respectively. TheRF circuit blocks 48-54 include suitable signal modulators anddemodulators, as appropriate. OBPs 56 and 58 are bidirectionallyconnected to the RF circuit blocks 48, 50 and 52, 54, respectively, andalso to the ICR 70.

The satellite 10 also includes, by example, a Ka-band or a C-band(feederlink) transmit antenna 60 and a Ka-band or a C-band receive(feederlink) antenna 62. For a presently preferred C-band embodiment thefeederlinks operate in the range of 3 GHz to 7 GHz. Coupled to antennas60 and 62 are respective RF circuit blocks 64 and 66, respectively. TheRF circuit blocks 64 and 66 include suitable signal modulators anddemodulators, as appropriate. The OBP 68 is bidirectionally connected tothe RF circuit blocks 64 and 66, and also to the ICR 70.

Turning now the ground segment 12, there are provided a plurality ofterrestrial data, or data and/or voice networks and also fixed andmobile user terminals. The ground segment 12 includes first gateways 72having transceivers for communicating with the satellite C-band antennas60 and 62. These transmissions are feederlinks through which voice anddata communications can be directed to and from a terrestrial publicswitched telephone network 74 (PSTN) and, by example, the user terminals82 and 84. The various terminals and other equipment designated as 78,80, 82 and 84 may all be considered to be subscriber or user terminalsor transceivers.

FIG. 2 shows the gateway 72 in greater detail, it being realized thattypically a plurality of the gateways are provided for serving differentgeographical areas. Each gateway 72 includes up to four dualpolarization RF C-band sub-systems each comprising an antenna 90,antenna driver 92 and pedestal 94, low noise receivers 96, and highpower amplifiers 98. All of these components may be located within aradome structure to provide environmental protection.

The gateway 72 further includes down converters 100 and up converters102 for processing the received and transmitted RF carrier signals,respectively. The down converters 100 and the up converters 102 areconnected to a CDMA sub-system 104 which, in turn, is coupled to thePublic Switched Telephone Network (PSTN) though a PSTN interface 106. Asan option, the PSTN could be bypassed by using satellite-to-satellitelinks.

The CDMA sub-system 104 includes a signal summer/switch unit 104a, aGateway Transceiver Subsystem (GTS) 104b, a GTS Controller 104c, a CDMAInterconnect Subsystem (CIS) 104d, and a Selector Bank Subsystem (SBS)104e. The CDMA sub-system 104 is controlled by a Base Station Manager(BSM) 104f and functions in a manner similar to a CDMA-compatible (forexample, an IS-95 compatible) base station. The CDMA sub-system 104 alsoincludes the required frequency synthesizer 104g and possibly a GlobalPositioning System (GPS) receiver 104h.

The PSTN interface 106 includes a PSTN Service Switch Point (SSP) 106a,a Call Control Processor (CCP) 106b, a Visitor Location Register (VLR)106c, and a protocol interface 106d to a Home Location Register (HLR).The HLR may be located in a cellular gateway or in the PSTN interface106.

The gateway 72 is connected to telecommunication networks through astandard interface made through the SSP 106a. The gateway 72 provides aninterface and connects to the PSTN via a Primary Rate Interface (PRI),or other suitable means. The gateway 72 is further capable of providinga direct connection to a Mobile Switching Center (MSC).

The gateway 72 may provide SS-7 ISDN fixed signalling to the CCP 106b.On the gateway-side of this interface, the CCP 106b interfaces with theCIS 106d and hence to the CDMA sub-system 104. The CCP 106b providesprotocol translation functions for the system Air Interface (AI), whichmay be similar to the IS-95 Interim Standard for CDMA communications.

Blocks 106c and 106d generally provide an interface between the gateway72 and an external cellular telephone network that is compatible, forexample, with the IS-41 (North American Standard, AMPS) or the GSM(European Standard, MAP) cellular systems and, in particular, to thespecified methods for handling roamers, that is, users who place callsoutside of their home system.

Overall gateway control is provided by a gateway controller 108 whichincludes an interface 108a to a Ground Data Network (GDN) 110 whichinterconnects the various gateways one to another and to GroundOperations Control Center (GOCC) 112. An interface 108b to a ServiceProvider Control Center (SPCC) 114 can also be provided. The gatewaycontroller 108 is generally interconnected to the gateway 72 through theBSM 104f and through RF controllers 116 associated with each of theantennas 90. The gateway controller 108 is further coupled to a database118, such as a database of users, satellite ephemeris data, etc., and toan I/O unit 120 that enables service personnel to gain access to thegateway controller 108.

Referring now again to FIG. 1, the ground segment 12 further includes afixed terrestrial network having a second gateway 76 that isbidirectionally connected to the Ka-band antennas 44 and 46 of thesatellite 10. Gateway 76 is also connected to the PSTN 74 and is alsoconnected to a fiber optic network 75 through a suitable fiber opticinterface. The gateway 76 can communicate with a number of differenttypes of equipment such as data processors (e.g., multimedia PCs 78having a suitable RF interface 78a connected to a suitable RF front end78b and a Ka-band antenna 78c). Other devices, such as userentertainment equipment 80 (e.g. television) can also be accommodated.The other devices can also be interfaces to a wireless local loop (WLL)of a type that serves an office building, residential area, etc. Inthese cases the other equipment 80 is also provided with suitable RFcircuitry and a Ka-band antenna 80a. The units 78 and 80 can beconsidered to form one or more virtual mesh, star or other network typeshaving a capability to be interconnected via the satellites 10, gateway76, the PSTN 74, and the fiber optic network 75. By example only, a 400MHz bandwidth, 1 MB/sec data link capability is provided between theunits 78, 80 and the second gateway 76, thereby enabling the deliveryof, by example, video, image and Internet services.

In accordance with an aspect of this invention the system disclosed inFIG. 1 can provide a global, wideband Internet access capability withnegligible connectivity time. The invention also enables a direct videodownload to a TV/PC, enables the use of interactive video, and alsoenables 2-way videophone capability. Interoperability with mobilecommunication devices 82 and 84 (e.g., handheld or fixed user terminals)is also provided (via the first gateway 72 or the second gateway 76), asis interoperability with various terrestrial wireless local loopsystems.

Reference is now made to FIG. 3 for illustrating a further aspect of theinstant invention. The sphere generally indicates the surface of theearth over which traverse a plurality of the LEO satellites 10. Eachsatellite 10 has a beam coverage area on the surface of the earthindicated generally as 10a. The beam coverage areas may overlap, thusproviding for diversity reception by user terminals and other equipmentlocated within the overlap region. Also shown are a plurality of theother satellites 11 which are in a higher orbit, such a geosynchronousorbit (GSO) or a medium-earth orbit (MEO). Other orbits, such as aMolniya orbit, can also be used. Each satellite 11 has a correspondinglarger coverage region indicated by 11a.

In this aspect of the invention the LEO satellites 10 are connected to,by example, the GSO satellites 11 via the inter-satellite links (ISL).In this manner transmissions from the region 10a can be relayed to thelarger region 11a, and vice versa. The regions can be closely spacedapart, or can be located on opposite sides of the earth.

Reference in this regard can also be made to FIG. 4 for illustratingvarious types of interconnectivity between and functionality of thevarious terrestrial terminals and the LEO constellation, either directlyor via the synchronous or other constellation type. By example, theblock 122, designated First Mobile Circuit Switched, communicates usingthe L-band and S-band satellite antennas 24 and 26 of FIG. 1, and caninclude mobile voice, cellular extension, GSM compatibility, and worldroaming. The block 124, designated Second Mobile Circuit Switched,communicates using the S-band satellite antennas 20 and 22 of FIG. 1,and can include mobile voice, PCS extension, FPLMTS compatibility, andworld roaming. The block 126, designated Fixed Circuit Switched,communicates using the Ka-band satellite antennas 40 and 42 of FIG. 1,and can include fixed voice and data, fiber optics extension, mediumspeed data, private networks, and internet services. The block 128 (alsoKa-band), designated International Circuit Switched, communicates via,by example, the GSO constellation and can provide a transport facility,an extended circuit switched network, international long lines, privatenetworks, and international Internet. The block 130, designatedInternational Wideband and Video, can include international video andwideband data distribution, regional video, and wideband data. The block132, designated Domestic Wideband and Video, can provide domestic videoand wideband data distribution. All of these various functions andfeatures can be simultaneously active and interconnected through theconstellation of LEO satellites 10 and the GSO (or other constellationtype) satellites 11 via the ISL. It should be noted in FIG. 4 thatinter-satellite links are also preferably provided between the GSOsatellites 11.

FIG. 5 illustrates an exemplary case where fiber optic cables are routedbetween major cities and metropolitan areas. Within the major cities andmetropolitan areas an extensive fiber optic infrastructure may exist.Between these areas the fiber optic service is only marginally provided,such as in the smaller city and town regions that are tapped into thefiber optic trunks that interconnect the larger cities and metropolitanareas. Other areas have no local fiber optic service. However, and inaccordance with an aspect of this invention, the satellite service area10a covers this region of little or no fiber optic service and providesan equivalent service via the fixed portion of the ground network 12shown in FIG. 1 (i.e., the gateway 76, Ka links, satellites 10, andterminals 78 and 80).

FIG. 6 illustrates the connectivity between various digitalTV/computers, the satellite 10, and local and long distance fiber opticnetworks. As can be seen, the digital TV/computer designated 140 has adirect connection (DC) to a local fiber-optic line and network which inturn is connected through a telephone or cable company 142 to a regionalfiber network. The regional fiber network is connected via a longdistance or cable company 144 to a long distance fiber network. The longdistance fiber network is connected to a further telephone or cablecompany 146 (or other entity) which in turn is connected to adistribution node 148. The distribution node 148 includes the gateway 76and is thereby connected via one or more of the satellites 10 (or one ofthe GSO or MEO satellites 11) to the antenna 78c, RF section 78b andinterface 78a of the PC 78 (refer also to FIG. 1). The connectionbetween the antenna 78c and the RF section 78b can be a wired or awireless connection. In this manner, the PC 78 is enabled to be coupledto the fiber network in essentially the same manner as the digitalTV/computer 140 which has a direct connection to the fiber-opticnetwork, and is thus enabled to avail itself of network and otherservices that are best served by the higher data rates made available byfiber optic lines.

The PC 78 can thus be connected to others of similar type in a meshnetwork, or in a star network, to the distribution node 148 and thenceto the serving entity such as the telephone or cable company. Furtherconnections to the PSTN can also be made. The further connections can beto other computers of similar type, to servers and/or to largercomputers providing network (e.g., Internet) services.

The antenna 78c may be directional, but is preferably omni-directionalwith hemispherical or semi-hemispherical coverage.

The use of the LEO constellation of satellites 10 provides uniqueadvantages when employed with the teaching of this invention. Consider amobile terminal which is moving under a tree (or other RF obstacle, suchas a building) and is blocked to one of several satellites 10 servingthe user (i.e., assume that the mobile terminal is located in theoverlap region of the coverage areas shown in FIG. 3). The use ofdiversity combining from those satellites that are not blocked providesimproved service and connectivity to the satellite constellation. It canbe shown that this performance increase is significant and providesmitigation of shadowing and blocking due to movement of the userterminal. In this regard the disclosure of U.S. Pat. No. 5,233,626,issued Aug. 3, 1993, entitled "Repeater Diversity Spread SpectrumCommunication System", to Stephen A. Ames is incorporated by referenceherein in its entirety for illustrating suitable embodiments of areceiver employing diversity combining.

When considering a LEO fixed system, the rain attenuation can be severein the frequency bands above 3 GHz, and especially above 10 GHz. Rainfades of 20 db or more occur in the Ka band frequencies. It is widelyknown that the availability of satellite systems to deliver signals ofthe desired strength is affected by these rain fades. It is also knownby experimentation that the duration and fade depth is affected by therainfall zone that the user is in (deserts have much improvedavailability as compared to tropical forest areas). Furthermore, "raincells", i.e., local rain zones around the user, have characteristicswhich cause rapidly changing conditions near user sites. In fact, forfixed locations operating with GSO satellites a significant amount ofanalysis has been done in predicting the availability of signals due torain attenuation. Since the rain cells cannot be avoided a certainpercentage of the time from coming between the fixed user and a GSOsatellite there is not much the fixed user can do to compensate for therain fade. In the past, it has been known to provide excessive margin topartially overcome theses attenuations, and in some cases to utilizeanother site located 35 to 50 or more miles away, to provide a"diversity" site. Switching between these two sites can increase thesystem signal availability. However, for a home or office user it is notpractical to provide such a diversity site.

In accordance with an aspect of this invention, by providing more signalpaths to the user from two or more of the satellites 10 at different andchanging azimuth and elevation angles, the effect is to provide the"diversity site" at a single location. In effect it is the opposite ofthe mobile user moving under the blocking obstruction, as the rain cellmoves with respect to the user terminal site. One suitablediversity-type of receiver is described in the above-mentioned U.S. Pat.No. 5,233,626, issued Aug. 3, 1993, entitled "Repeater Diversity SpreadSpectrum Communication System, to Stephen A. Ames.

Although described above in the context of specific frequency bands,bandwidths, data rates and the like, it should be realized that theseare exemplary, and not limiting, embodiments of this invention. Byexample only, one or more of the Ka-band links shown in FIG. 1 could bereplaced by a Ku-band link. Furthermore, the teaching of this inventioncan be practiced with but one LEO satellite, or with one LEO satelliteand one GSO or MEO satellite. However, it is preferred to use largernumbers of satellites to provide a wide area coverage, while alsoenabling the use of the above-mentioned diversity reception techniquesby the subscriber terminals and equipment.

Thus, while the invention has been particularly shown and described withrespect to preferred embodiments thereof, it will be understood by thoseskilled in the art that changes in form and details may be made thereinwithout departing from the scope and spirit of the invention.

What is claimed is:
 1. A communications system, comprising:at least onelow earth orbit first satellite; at least one second satellite in otherthan a low earth orbit; and a ground segment comprising a plurality ofuser transceivers and at least one gateway coupled to a terrestrialcommunications system; wherein said first satellite comprises a firsttransceiver for communication with said at least one gateway, a secondtransceiver for communication with at least one user transceiver, and athird transceiver for communication with said at least one secondsatellite, said first, second and third transceivers being switchablycoupled together on-board said first satellite for relaying a usercommunication between said at least one gateway and said at least oneuser transceiver via said at least one second satellite.
 2. Acommunications system as set forth in claim 1, wherein said at least onefirst satellite further comprises a first on-board processor that isbidirectionally coupled to said first transceiver; a second on-boardprocessor that is bidirectionally coupled to said second transceiver;and a switching network that is bidirectionally coupled to said firstand second on-board processors and to said third transceiver forselectively establishing communication paths between said first andsecond on-board processors and said third transceiver.
 3. Acommunications system as set forth in claim 1, wherein said terrestrialcommunications system is comprised of a fiber optic network that isbidirectionally coupled to said at least one gateway.
 4. Acommunications system as set forth in claim 1, wherein said plurality ofuser transceivers are comprised of a plurality of data processors, andwherein said plurality of data processors are interconnected into anetwork through said at least one first satellite.
 5. A communicationssystem as set forth in claim 1, wherein said plurality of usertransceivers are adapted to transmit and receive direct sequence, codedivision/multiple access communications.
 6. A communications system,comprising:at least one low earth orbit first satellite; at least onesecond satellite in other than a low earth orbit; and a ground segmentcomprising a plurality of user transceivers and at least one gatewaycoupled to a terrestrial communications system comprised of fiber opticinfrastructure, said at least one gateway comprising a gatewaytransceiver for bidirectionally coupling said at least one gateway tosaid at least one first satellite; wherein a plurality of said usertransceivers each comprises a data processor that is bidirectionallycoupled to said fiber optic infrastructure through at least one of saidfirst and second satellites and said at least one gateway; wherein saidat least one first satellite comprises a first transceiver forcommunication with said at least one gateway, a second transceiver forcommunication with at least one user transceiver, and a thirdtransceiver for communication with said at least one second satellite,said first, second and third transceivers being switchably coupledtogether on-board said first satellite for relaying a user communicationbetween said at least one gateway and said at least one user transceivervia said at least one second satellite.
 7. A communications system asset forth in claim 6, wherein said at least one gateway transmitsdigital information to and receives digital information from said atleast one satellite, the digital information being comprised of at leastone of voice, data, video and image.
 8. A communications system as setforth in claim 6, wherein said at least one first satellite furthercomprises a first on-board processor that is bidirectionally coupled tosaid first transceiver; a second on-board processor that isbidirectionally coupled to said second transceiver; and a switchingnetwork that is bidirectionally coupled to said first and secondon-board processors and to said third transceiver for selectivelyestablishing communication paths between said first and second on-boardprocessors and said third transceiver.
 9. A communications system as setforth in claim 6, wherein said terrestrial communications system iscomprised of a public switched telephone network.
 10. A communicationssystem as set forth in claim 7, wherein said at least one gatewaytransmits and receives the digital information using a direct sequence,code division/multiple access technique.
 11. A communications system,comprising:a first constellation of earth orbiting satellites; a secondconstellation of earth orbiting satellites, said second constellationorbiting at a higher altitude than said first constellation; a pluralityof terrestrial mobile user terminals each comprising a transceiver forbidirectionally coupling said mobile user terminal to at least onesatellite of said first constellation using a first band of frequencies;a plurality of terrestrial fixed user terminals each comprising atransceiver for bidirectionally coupling said fixed user terminal to atleast one satellite of said first constellation using a second band offrequencies; at least one first gateway that is bidirectionally coupledto a first terrestrial communication network, said at least one firstgateway comprising a transceiver for bidirectionally coupling said firstgateway to at least one satellite of said first constellation using athird band of frequencies; and at least one second gateway that isbidirectionally coupled to a second terrestrial communication networkthat comprises a fiber optic infrastructure portion, said at least onesecond gateway comprising a transceiver for bidirectionally couplingsaid second gateway to at least one satellite of said firstconstellation using a fourth band of frequencies; wherein each of saidsatellites of said first constellation is comprised of a plurality oftransceivers operable within said first, second, third, and fourthfrequency bands, a further transceiver operable for providing aninter-satellite link with said at least one satellite of said secondconstellation, a plurality of on-board processors that arebidirectionally coupled to said plurality of transceivers, a switchingmatrix that is bidirectionally coupled to each of said plurality ofon-board processors and to said further transceiver for selectablycoupling individual ones of said plurality of on-board processors andsaid further transceiver together for routing communication signalsbetween said plurality of transceivers and said further transceiver. 12.A communications system as set forth in claim 11, wherein said firstband of frequencies includes frequencies in at least one of S-band andL-band, wherein said second band of frequencies includes frequencies inat least one of Ka-band and Ku-band, wherein said third band offrequencies includes frequencies in a C-band or Ka band, and whereinsaid fourth band of frequencies includes frequencies in at least one ofKa-band and Ku-band.
 13. A communications system as set forth in claim11, wherein said first terrestrial communications system is comprised ofa public switched telephone network.
 14. A communications system as setforth in claim 11, wherein said transceivers of said at least one firstand second gateways transmit and receive RF signals using a directsequence, code division/multiple access technique.
 15. A communicationssystem as set forth in claim 11, wherein said transceivers of said atleast one first and second gateways transmit and receive RF signals thatare modulated to convey digital information comprised of at least one ofvoice, data, video and image.
 16. A communications system, comprising:atleast one first satellite in a non-geosynchronous orbit; at least onesecond satellite in a higher orbit than said first satellite; and aground segment comprising a plurality of user transceivers and at leastone gateway coupled to at least one terrestrial communications system,said gateway having an associated service region within which at leastone of said user transceivers is located; wherein said first satellitecomprises a first transceiver for communication with said gateway, asecond transceiver for communication with said at least one usertransceiver, and a third transceiver for communication with said secondsatellite, said first, second and third transceivers being switchablycoupled together on-board said first satellite for relaying acommunication between said gateway and said user transceiver via saidsecond satellite, wherein said relayed communication is comprised of adata communication.
 17. A communications system, comprising:at least onefirst satellite in a non-geosynchronous orbit; at least one secondsatellite in a higher orbit than said first satellite; and a groundsegment comprising a plurality of user transceivers and at least onegateway coupled to at least one terrestrial communications system, saidgateway having an associated service region within which at least one ofsaid user transceivers is located; wherein said first satellitecomprises a first transceiver for communication with said gateway, asecond transceiver for communication with said at least one usertransceiver, and a third transceiver for communication with said secondsatellite, said first, second and third transceivers being switchablycoupled together on-board said first satellite for relaying acommunication between said gateway and said user transceiver via saidsecond satellite, wherein said relayed communication is comprised of avideo communication.
 18. A communications system, comprising:at leastone first satellite in a non-geosynchronous orbit; at least one secondsatellite in a higher orbit than said first satellite; and a groundsegment comprising a plurality of user transceivers and at least onegateway coupled to at least one terrestrial communications system, saidgateway having an associated service region within which at least one ofsaid user transceivers is located; wherein said first satellitecomprises a first transceiver for communication with said gateway, asecond transceiver for communication with said at least one usertransceiver, and a third transceiver for communication with said secondsatellite, said first, second and third transceivers being switchablycoupled together on-board said first satellite for relaying acommunication between said gateway and said user transceiver via saidsecond satellite, wherein said relayed communication is comprised of acircuit switched connection.
 19. A communications system, comprising:atleast one first satellite in a non-geosynchronous orbit; at least onesecond satellite in a higher orbit than said first satellite; and aground segment comprising a plurality of user transceivers and at leastone gateway coupled to at least one terrestrial communications system,said gateway having an associated service region within which at leastone of said user transceivers is located; wherein said first satellitecomprises a first transceiver for communication with said gateway, asecond transceiver for communication with said at least one usertransceiver, and a third transceiver for communication with said secondsatellite, said first, second and third transceivers being switchablycoupled together on-board said first satellite for relaying acommunication between said gateway and said user transceiver via saidsecond satellite, wherein said relayed communication is comprised of anInternet connection.
 20. A communications system, comprising:a pluralityof first satellites in a non-geosynchronous orbit; at least one secondsatellite in a higher orbit than said plurality of first satellites; anda ground segment comprising a plurality of user transceivers and atleast one gateway coupled to at least one terrestrial communicationssystem, said gateway having an associated service region within which atleast one of said user transceivers is located; wherein each of saidfirst satellites comprises a first transceiver for communication withsaid gateway, a second transceiver for communication with said at leastone user transceiver, and a third transceiver for communication withsaid second satellite, said first, second and third transceivers beingswitchably coupled together on-board each of said first satellites forselectively routing a communication between said gateway and said usertransceiver, wherein a communication is simultaneously routed through atleast two of said first satellites, wherein said user transceivercomprises means for combining a communication that is simultaneouslyreceived from said at least two of said first satellites, and whereinsaid routed communication is comprised of at least one of a circuitswitched connection, a data connection, or a video connection.